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VSMEF016 Referenced metadata view interface should be source-generated

VSMEF016 warns when a C# import uses a metadata view interface declared in another assembly, but that referenced assembly did not emit MetadataViewImplementationAttribute for the interface.

Why this matters

VS MEF now generates metadata view implementations only in the assembly that declares the interface. Consuming assemblies do not generate implementations for referenced interfaces.

How to fix it

Recompile the assembly that declares the interface:

  1. Add a reference to the Microsoft.VisualStudio.Composition package to that project, if missing.
  2. Apply MetadataViewAttribute to the interface.
  3. Declare the interface partial.

After that assembly is rebuilt, consumers will observe the generated MetadataViewImplementationAttribute automatically.

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